1. Field of the Invention
This invention concerns a photosensitive type resin composition and, more specifically, it relates to a positive type photosensitive resin composition having improved adhesion to a substrate and developing properties.
2. Description of Prior Arts
In the production of semiconductors, printed circuit boards, printing plates, etc., etching, plating, diffusion or other similar treatments have generally been applied. When applying such treatments, it is generally necessary to protect a portion of the substrate. As a means for selectively protecting the surface of the substrate, the standard practice has been, for instance, to coat the substrate with a photosensitive resin (hereinafter simply referred to as a "photoresist"), irradiate with actinic rays projected through a predetermined original film and then apply a developing treatment to form a resist pattern on the substrate. Then, various treatments such as etching, plating and diffusion as described above have generally been applied using the thus obtained resist pattern as a mask.
Known photoresists include a negative type in which a resist pattern is formed by dissolving and removing a non-irradiated portion with a liquid developer, utilizing the property that the irradiated portion hardens into an insoluble state, and a positive type in which a resist pattern is formed, conversely, by dissolving and removing an irradiated portion. The positive type photoresist is noted for its capacity to perform in a smaller scale which is the trend in the fabrication size. It has greater resolution power, yields sharper images than the negative type photoresist, is free from the effects of oxygen upon irradiation of actinic rays, and has excellent stability after coating. However, for coping with the size-reducing trend in fabrication, close bondability to the substrate is extremely important in addition to the resolution power of the positive type photoresist and it is necessary that the resist pattern be firmly bonded to the substrate with no ready separation during treatments such as developing or etching. In view of the above, conventional positive type photoresists are not sufficient and can not cope with the size-reducing trend in the fabrication.
For improving the adhesive property of the positive type photoresist to the substrate, a positive type photoresist has already been developed; incorporated with a compound obtained by reacting an addition product of a conjugated diene polymer with .alpha.,.beta.-unsaturated dicarboxylic acid or the anhydride thereof and a compound having an alcoholic hydroxy group thereby conducting partial esterification (refer, for example, to Japanese Patent Kokai No. Sho 59-170836), as well as a positive type photoresist incorporated with a compound obtained from an unsaturated dicarboxylic acid and ethylene glycol through polycondensating reaction (refer, for example, to Japanese Patent Kokai No. Sho 58-172643), etc.
However, even these known techniques do not always provide a sufficient adhesive property to the substrate for coping with the size-reducing trend in fabrication at present and, if the polymer type compound is added for the improvement of the adhesive property, there is an additional problem. The developing property of the positive type photoresist is worsened and the portion irradiated with the actinic rays can not be completely removed by the liquid developer upon developing treatment thereby resulting in residual resist.
Further, for improving the adhesiveness of a negative type photoresist to a substrate, a negative type photoresist has also been developed containing a compound selected from the group consisting of benzotriazole, benzoimidazole, benzothiazole, derivatives and salts thereof, and a phosphoric acid compound having a photopolymerizable unsaturated bonds (refer, for example, to Japanese Patent Kokai No. Sho 58-24035 and U.S. Patent Specification No. 4438190).
However, although the adhesion between the negative type photoresist and the substrate can be improved to some extent due to the property of the added compound benzotriazole of intensely bonding to the substrate in the prior art, there is still at present a drawback; the portion irradiated by the actinic rays can not completely be removed upon developing treatment resulting in a great amount of residual resist (that is, remarkably poor developing property).